1. Field of the Invention
The present invention generally relates to electrodes for sensing or stimulating or both, and more particularly the present invention relates to electrodes and sensors carried on a flexible substrate. Still more particularly the present invention relates to respiration sensor technology for detecting abnormal breathing of a client.
2. Description of the Prior Art
It is known in the prior art to employ respiration sensors to monitor patients' susceptible to sleep apnea and other disorders of the respiration system. U.S. Pat. No. 4,878,502 discusses a breathing sensor employing a tubular passage in which a ball is free to move to break a beam of light. The ball is moved in response to the flow of air associated with the breathing of a patient. An optoelectric inhalation sensor using thin film deposition is disclosed in U.S. Pat. No. 4,745,925.
Acoustic sensors for monitoring respiration are mentioned in U.S. Pat. Nos. 4,602,664 and 4,595,016. U.S. Pat. No. 4,366,821 shows a respiration monitoring system that preferably uses a gas sensor, and U.S. Pat. No. 4,350,166 discloses the use of a video monitor. U.S. Pat. No. 4,326,404 discloses the use of a sodium chloride crystal to sense moisture.
A pressure sensor for respiration monitoring is taught in U.S. Pat. No. 4,306,867. U.S. Pat. No. 4,289,142 teaches the use of an impedance plethysmograph for respiration sensing. The use of thermoresistive sensors for monitoring is suggested in U.S. Pat. Nos. 3,903,876; 3,884,219; and 3,999,537.
The advantages of providing multiple sensors on a single flexible substrate are taught in U.S. patent application Ser. No. 08/182,424, filed Jan. 18, 1994 by Bowman et al. This Bowman et al Application discusses employing a plurality of sensor electrodes positioned at the various orifices which vent the upper airway of a patient; normally the two nostrils and the mouth.
A continuing disadvantage with this and other prior art which employs flexible substrates is that when the substrate is flexed, the resulting pressure on the sensor electrodes causes changes in their electrical and thermoresistive specifications.